You should be able to answerr this yourself better than we can answer it for you.
- Did you like the functionality of the included dreams?
- Do you wnat more dreams?
- Have you looked at what's available in the Wincustomize Dream gallery?
- Do any of those appeal to you?
If you answered yes to those questions ask yourself if it is worth X of some other thing you like. If you like fancy coffee at $4 a cup, are the dreams available worth four of them?
In regards to the premium dreams . . take a look at the previews. Are they attractive enough to pay for the extra work that the creators put into it? If not, don't bother. If so, is whichever dream worth the trade.
I think the ability to play other dreams is worth it. And I have bought a few of the premium dreams.